Carbon nanotube device and manufacturing method of the same

ABSTRACT

After forming an opening, a resist film is formed on the entire surface and a resist pattern is formed by patterning the resist film. The shape of the resist pattern is such that it covers one side of the bottom of the opening. As a result, a Si substrate is exposed only in one part of the opening. Then, using the resist pattern as a mask, a catalytic layer is formed on the bottom of the opening. Then, the resist pattern is removed. Carbon nanotubes are grown on the catalytic layer. At this time, since the catalytic layer is formed on only one side of the bottom of the opening, the Van der Waals force biased towards that side works horizontally on the growing carbon nanotubes. Therefore, the carbon nanotubes are attracted towards the nearest side of the SiO 2  film and grow biased towards that side.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2005-080519, filed on Mar. 18,2005, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a carbon nanotube device suitable forintegrated circuits and the like and a manufacturing method of the same.

2. Description of the Related Art

In recent years, many researches have been directed to application of acarbon nanotube to semiconductor devices. As a method of obtaining acarbon nanotube, a catalytic layer is arranged in a hole formed in aninsulating film, and the carbon nanotubes are grown vertically from thecatalytic layer as shown in FIG. 11A, FIG. 11B, FIG. 12A and FIG. 12B.

In addition to the above method, there is a method of growing a carbonnanotube in a horizontal direction. This method will be explained. FIG.13 is a view showing a method of growing the carbon nanotubehorizontally. A laminate of a titanium (Ti) film 102 and a cobalt (Co)film 103 is formed at two spots on a silicon (Si) substrate 101 inadvance. An electric field is applied between these two spots to grow acarbon nanotube 104. As a result, as shown in FIG. 13, the carbonnanotubes 104 running along the direction of the electric field appliedthereto are formed.

However, there is a limitation in shape of the carbon nanotube formedaccording to these methods only. Furthermore, under a circumstance whereno electric field is applied, it is impossible to connect between twospots existing apart from each other horizontally by the carbonnanotubes.

Related arts are disclosed in Japanese Patent Application Laid-open No.2004-181620 (Patent Document 1), and Japanese Patent ApplicationLaid-open No. 2004-174637 (Patent Document 2).

SUMMARY OF THE INVENTION

The present invention is made in view of the aforementioned problems,and its object is to provide a carbon nanotube device having a highdegree of freedom in the shape of the carbon nanotube and amanufacturing method of the same.

As a result of earnest studies to solve the above-described problems,the present inventors have arrived at several aspects of the presentinvention as shown below.

A carbon nanotube device according to the present invention includes acatalytic layer, a body positioned around the catalytic layer, and acarbon nanotube grown along the body from the catalytic layer. Thecarbon nanotube is curved at a corner of the body.

In a manufacturing method of the carbon nanotube according to thepresent invention, after a catalytic layer and a body extending to aposition above the catalytic layer around the catalytic layer areformed, a carbon nanotube is grown from the catalytic layer along thebody while being bent by the effect of the Van der Waals force from thebody.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A to FIG. 1C are sectional views showing a manufacturing method ofa carbon nanotube device according to a first embodiment of the presentinvention in process order;

FIG. 2A is an SEM photograph showing carbon nanotubes grown from anopening;

FIG. 2B is a schematic view showing the contents of the SEM photographshown in FIG. 2A;

FIG. 3A is an SEM photograph showing carbon nanotubes grown from aplurality of openings;

FIG. 3B is a schematic view showing the contents of the SEM photographshown in FIG. 3A;

FIG. 4A to FIG. 4C are sectional views showing a manufacturing method ofa carbon nanotube device according to a second embodiment of the presentinvention in process order;

FIG. 5A is an SEM photograph showing carbon nanotubes grown from aT-shaped groove in plane view;

FIG. 5B is a schematic view showing the contents of the SEM photographshown in FIG. 5A FIG. 6A is an SEM photograph enlargedly showing a bentportion on the right side of FIG. 5A;

FIG. 6B is a schematic view showing the contents of the SEM photographshown in FIG. 6A;

FIG. 7A and FIG. 7B are sectional views showing a manufacturing methodof a carbon nanotube device according to a third embodiment of thepresent invention in process order;

FIG. 8A is an SEM photograph showing carbon nanotubes grown from anopening;

FIG. 8B is a schematic view showing the contents of the SEM photographshown in FIG. 8A;

FIG. 9A is an SEM photograph showing carbon nanotubes grown from aplurality of openings;

FIG. 9B is a schematic view showing the contents of the SEM photographshown in FIG. 9A;

FIG. 10 is a sectional view showing a carbon nanotube device accordingto a fourth embodiment of the present invention;

FIG. 11A is an SEM photograph of carbon nanotubes formed by aconventional method seen from above;

FIG. 11B is a schematic view showing the contents of the SEM photographshown in FIG. 11A;

FIG. 12A is an SEM photograph of carbon nanotubes formed by aconventional method seen from side;

FIG. 12B is a schematic view showing the contents of the SEM photographshown in FIG. 12A;

FIG. 13 is a view showing a conventional method with which carbonnanotubes are grown horizontally.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be concretelyexplained with reference to attached drawings. However, for convenience′sake, the structure of a carbon nanotube device will be explained whenthe manufacturing method of the same is explained.

First Embodiment

Firstly, a first embodiment of the present invention will be explained.FIG. 1A to FIG. 1C are sectional views showing a manufacturing method ofa carbon nanotube device according to the first embodiment of thepresent invention in process order.

In the first embodiment, as shown in FIG. 1A, a SiO₂ film 12 is firstformed on a silicon (Si) substrate 11. The SiO₂ film 12 is, forinstance, about 350 nm in thickness. Next, a cylindrical opening 13 isformed in the SiO₂ film 12 by patterning with a resist pattern (notshown). The opening 13 is, for instance, about 2 μm in diameter.

Then, a resist film is formed on the entire surface, and a resistpattern 16 is formed by patterning the resist film, as shown in FIG. 1B.The resist pattern 16 has a shape covering the bottom of the opening 13on only one side. As a result, the Si substrate 11 is exposed only froma part of the opening 13. In the present embodiment, especially when theresist pattern 16 is formed, a part of a side surface of the SiO₂ film12 is exposed without being covered by the resist pattern 16.

Then, as shown also in FIG. 1B, using the resist pattern 16 as a mask, acatalytic layer 14 is formed on the bottom of the opening 13. A cobalt(Co) film of, for instance, about 1 nm in thickness., is formed as thecatalytic layer 14. At this time, the catalytic layer 14 is not formedover the entire bottom of the opening 13 but only on the exposed part ofthe Si substrate 11.

Next, as shown in FIG. 1C, the resist pattern 16 is removed. Then,carbon nanotubes 15 are grown on the catalytic layer 14. At this time,since the catalytic layer 14 is formed biased towards one side in theopening 13, the Van der Waals force biased towards that side workshorizontally on the carbon nanotubes 15 in the growing process.Therefore, as shown in FIG. 1C, the carbon nanotubes 15 are attractedtowards the nearest side surface of the SiO₂ film 12 and grows biasedtowards that side. After they grow higher than the surface of the SiO₂film 12, the Van der Waals force nearly ceases to have effect. However,the inclination is succeeded as is. During further growth, the carbonnanotubes 15 are largely affected by their own weight, so that theirshape are significantly curved.

The SEM photographs of the carbon nanotubes actually taken by thepresent inventors are shown in FIG. 2A and FIG. 3A. FIG. 2A is an SEMphotograph showing carbon nanotube s grown from an opening, and FIG. 2Bis a schematic view showing the contents of the SEM photograph shown inFIG. 2A. FIG. 3A is an SEM photograph showing carbon nanotubes grownfrom a plurality of openings, and FIG. 3B is a schematic view showingthe contents of the SEM photograph shown in FIG. 3A.

After the carbon nanotubes 15 are formed as described above, requiredelements, wiring layers, insulating layers and the like are formed tocomplete a carbon nanotube device.

According to the first embodiment, the carbon nanotubes 15 can besubstantially grown in a direction parallel to the surface of the Sisubstrate 11 even without application of an electric field. In addition,since the carbon nanotubes 15 take a curved shape, the carbon nanotubescan be used extensively. For instance, a coil can be formed byconnecting a plurality of curved carbon nanotubes 15 to each other.

Second Embodiment

Next, a second embodiment of the present invention will be explainednext. FIG. 4A to FIG. 4C are sectional views showing a manufacturingmethod of a carbon nanotube device according to the second embodiment ofthe present invention in process order.

First, in the second embodiment, as shown in FIG. 4A, a catalytic layer24 is selectively formed on a Si substrate 21. As the catalytic layer24, for instance, a cobalt (Co) film having a thickness of about 1 nm isformed.

Next, a SiO₂ film 22 is formed over the entire surface thereof. Then, agroove 23 is formed in the SiO₂ film 22 by patterning using a resistpattern (not shown). The thickness of the SiO₂ film 22 is, for instance,about 350 nm. When forming the groove 23, as shown in FIG. 4B, both ofthe Si substrate 21 and the catalytic layer 24 are to be exposed fromthe groove 23.

Thereafter, as shown in FIG. 4C, carbon nanotubes 25 are grown on thecatalytic layer 24. At this time, since the catalytic layer 24 is notformed evenly on the entire bottom portion of the groove 23, but formedbiased towards one side in the present embodiment, the Van der Waalsforce biased towards that side works horizontally on the carbonnanotubes 25 in the growing process. Accordingly, as shown in FIG. 4C,the carbon nanotubes 25 are attracted to a nearest side surface of theSiO₂ film 22 and grow biasedly. After they grow higher than the surfaceof the SiO₂ film 22, the Van der Waals force scarcely works, but theinclination is succeeded as it is. When they further grow, a large ownweight works on the carbon nanotubes 25, so that the shape of the carbonnanotubes 25 are largely curved.

SEM photographs of the carbon nanotubes actually taken by the presentinventors are shown in FIG. 5A and FIG. 6A. FIG. 5A is an SEM photographshowing carbon nanotubes grown from a T-shaped groove in plane view, andFIG. 5B is a schematic view showing the contents of the SEM photographshown in FIG. 5A. FIG. 6A is an SEM photograph enlargedly shown a bentportion on the right side of FIG. 5A, and FIG. 6B is a schematic viewshowing the contents of the SEM photograph shown in FIG. 6A. Note thatin FIG. 5A and FIG. 5B, parts of the carbon nanotubes on the left aremissing. They were dropped out when handling before taking the SEMphotographs, which does not deny the effect of the present invention.

Thus, it is possible to obtain the same effect as that of the firstembodiment according to the second embodiment.

Third Embodiment

Next, a third embodiment of the present invention will be explainednext. FIG. 7A to FIG. 7B are sectional views showing a manufacturingmethod of a carbon nanotube device according to the third embodiment ofthe present invention in process order.

In the third embodiment, first, as shown in FIG. 7A, a copper (Cu) film32 and a tantalum (Ta) film 33 are formed in sequence on a Si substrate31 by, for instance, a sputtering method. The Cu film 32 and the Ta film33 are about 150 nm and about 5 nm in thickness, respectively. Then, aSiO₂ film 34 is formed over the entire surface. The SiO₂ film 34 is, forinstance, about 350 nm in thickness. Next, a cylindrical opening 38 isformed on the SiO₂ film 34 by patterning with a resist pattern (notshown). The opening 38 is, for instance, about 2 μm in diameter.

Then, similarly to the first embodiment, a resist film is formed on theentire surface, and a resist pattern (not shown) is formed by patterningthe resist film so that the Ta film 33 is exposed only from a part ofthe opening 38. When this resist pattern is formed, a part of a sidesurface of the SiO₂ film 34 is to be exposed without being covered bythe resist pattern in this embodiment. Then, using the resist pattern asa mask, a titanium (Ti) film 35 and a cobalt (Co) film 36 are formed insequence on the bottom of the opening 38. At this time, the Ti film 35and the Co film 36 are not formed over the entire bottom of the opening38 but only on a part where the Ta film 33 is exposed. Both the Ti film35 and the Co film 36 are about 1 nm in thickness. After forming the Tifilm 35 and the Co film 36, the resist pattern is removed.

Then, as shown in FIG. 7B, carbon nanotubes 37 are grown on the Co film36, which is a catalytic layer. At this time, since the Co film 36 isformed biased towards one side within the opening 38 in the presentembodiment, the Van der Waals force biased towards that side workshorizontally on the carbon nanotubes 37 which is in the process ofgrowing. Accordingly, as shown in FIG. 7B, the carbon nanotubes 37 areattracted to the nearest side surface of the SiO₂ film 34 and growbiased to that side. Thus, the shape of the carbon nanotubes 37 islargely curved similarly to the first and second embodiments.

SEM photographs of the carbon nanotubes actually taken by the presentinventors are shown in FIG. 8A and FIG. 9A. FIG. 8A is an SEM photographshowing carbon nanotubes grown from an opening, and FIG. 8B is aschematic view showing the contents of the SEM photograph shown in FIG.8A. FIG. 9A is an SEM photograph showing carbon nanotubes grown from aplurality of openings, and FIG. 9B is a schematic view showing thecontents of the SEM photograph shown in FIG. 9A.

It is possible to obtain the same effect as that of the first embodimentaccording to the third embodiment. In the third embodiment, by adjustingthe thickness of the Ti film 35 and the Co film 36, the growingconditions of the carbon nanotubes 37 can be controlled.

Fourth Embodiment

Next, a fourth embodiment of the present invention will be explained.FIG. 10 is a sectional view showing a carbon nanotube device accordingto the fourth embodiment of the present invention.

In the fourth embodiment, a catalytic layer 55 is formed on wiring 51buried in an insulating film 52. An insulating layer 54 is formed on thewiring 51 and the insulating film 52, and an opening reaching down tothe catalytic layer 55 is formed in the insulating film 54. Thecatalytic layer 55 is not formed on the entire bottom of the opening,but is located biased towards one side. Wiring 57 is formed on theinsulating film 54. The catalytic layer 55 and the wiring 57 areconnected by carbon nanotubes 56. An insulating film 58 covering thewiring 57 and the like is formed.

In the fourth embodiment like this, the carbon nanotubes 56 grown fromthe catalytic layer 55 to the wiring 57 function as a part of wiring.Since the resistance of the carbon nanotubes 56 is remarkably lowcompared with Cu and Al wiring, it is possible to realize a device witha low power consumption.

It should be noted that these embodiments are on an assumption thatcurved carbon nanotubes are used inside an integrated circuit chip, itis also possible to use curved carbon nanotubes as wiring to connect anelectrode of an integrated circuit chip and a lead frame. In addition,curved carbon nanotubes can be applied to an electron source, aconnector, a heating device and the like.

As a catalytic layer, an iron (Fe) film or a nickel (Ni) film may beused as well as the Co film. An alloy film of these metals can also beused. Further, a body in which metal fine particles containing Co, Feand/or Ni are carried by alumina, silica, magnesia or zeolite can beused.

Additionally, a body exerting the Van der Waals force on carbonnanotubes is not limited to an insulating film. As an insulating film, asilicon nitride film can also be used other than the above-describedsilicon oxide film. Furthermore, silicon-based porous low dielectricconstant film, fluorocarbon-based low dielectric constant film andresin-based low dielectric constant film can also be used.

Note that it is disclosed in Patent Document 1 that a carbon nanotubecan be bent by adjusting the thickness of a catalytic layer, constituentelements and the like. However, this is an impracticable method, becausemuch trial and error is required to obtain an appropriate degree ofcurvature. On the other hand, in the present invention, it is possibleto change the direction of the bending and the curvature of a carbonnanotube by changing at least either the thickness (height) of thesilicon oxide film or the distance between the catalytic layer and theside surface of the opening. Therefore, it is easy to adjust the degreeof curvature.

A carbon nanotube having a curved shape can be obtained according to thepresent invention. Therefore, the freedom of shape is improved and therange of application can be widened. Additionally, it is possible togrow a carbon nanotube in an arbitrary direction without applying anelectric field.

The present embodiments are to be considered in all respects asillustrative and no restrictive, and all changes which come within themeaning and range of equivalency of the claims are therefore intended tobe embraced therein. The invention may be embodied in other specificforms without departing from the spirit or essential characteristicsthereof.

1. A carbon nanotube device, comprising: a catalytic layer; a bodysituated around said catalytic layer; and a carbon nanotube grown alongsaid body from said catalytic layer, said carbon nanotube being curvedat a corner of said body.
 2. The carbon nanotube device according toclaim 1, wherein said body is an insulating film.
 3. The carbon nanotubedevice according to claim 2, wherein said insulating film is a siliconoxide film or a silicon nitride film.
 4. The carbon nanotube deviceaccording to claim 2, wherein said insulating film is a low dielectricconstant film.
 5. The carbon nanotube device according to claim 4,wherein said low dielectric constant film is one kind of films selectedfrom the group consisting of a porous silicon-based film, afluorocarbon-based film, and a resin-based film.
 6. The carbon nanotubedevice according to claim 2, wherein an opening is formed in saidinsulating film, and said catalytic layer is formed on only one side insaid opening when seen in plane view.
 7. The carbon nanotube deviceaccording to claim 1, wherein said catalytic layer contains at least onekind of metal elements selected from the group consisting of cobalt(Co), iron (Fe) and nickel (Ni).
 8. The carbon nanotube device accordingto claim 1, wherein said catalytic layer contains fine particles of acatalytic metal.
 9. The carbon nanotube device according to claim 1,wherein said carbon nanotube functions as a component of wiring.
 10. Thecarbon nanotube device according to claim 1, wherein said carbonnanotube functions as a part of a coil.
 11. The carbon nanotube deviceaccording to claim 1, wherein said carbon nanotube is connected to alead frame.
 12. A manufacturing method of a carbon nanotube device,comprising the steps of: forming a catalytic layer and a body extendingto a position above said catalytic layer around said catalytic layer;and growing a carbon nanotube from said catalytic layer along said bodywhile being bent by the effect of the Van der Waals force from saidbody.
 13. The manufacturing method of the carbon nanotube deviceaccording to claim 12, wherein the step of forming said catalytic layerand said body comprise the steps of: forming an insulating film as saidbody on or above a substrate; forming an opening in said insulatingfilm; and forming said catalytic layer on the bottom of said opening.14. The manufacturing method of the carbon nanotube device according toclaim 13, wherein said catalytic layer is formed on only one side insaid opening in plane view, in the step of forming said catalytic layeron the bottom of said opening.
 15. The manufacturing method of thecarbon nanotube device according to claim 12, wherein the step offorming said catalytic layer and said body comprise the steps of:forming said catalytic layer on or above a substrate; forming aninsulating film covering said catalytic layer as said body; and formingan opening reaching down to said catalytic layer in said insulatingfilm.
 16. The manufacturing method of the carbon nanotube deviceaccording to claim 15, wherein said catalytic layer is exposed in a partof said opening, in the step of forming said opening.
 17. Themanufacturing method of the carbon nanotube device according to claim13, wherein a silicon oxide film or a silicon nitride film is formed assaid insulating film.
 18. The manufacturing method of the carbonnanotube device according to claim 13, wherein a low dielectric constantfilm is formed as said insulating film.
 19. The manufacturing method ofthe carbon nanotube device according to claim 18, wherein one kind offilms selected from the group consisting of a porous silicon-based film,a fluorocarbon-based film and a resin-based film as said low dielectricconstant film.